The subject matter described herein relates generally to methods and systems for controlling power plants to influence the characteristics of high voltage (HV) power lines at points-of-interconnection to a grid, and more particularly, to methods and systems for controlling renewable-power plants such as wind energy power plants.
A power plant has to meet the characteristics, i.e., the operating parameters, defined by the grid code to ensure proper functioning of the electrical grid. Power producers like photovoltaic power stations or wind farms have to comply with the grid code. In particular, compliance with the grid code requires that the electrical characteristics meet those prescribed by the grid code at the point-of-interconnection (POI) to the grid. The POI is typically at the high-voltage (HV) side. The HV side is separated from the medium voltage (MV) side by a transformer which transforms medium voltage at the MV side to high voltage at the HV side.
For conformance with the grid code voltage and current may be measured on an HV power line, and the measurement values may be used to control the power plant in order to influence or regulate the electrical characteristics of the HV power line at the HV side before the POI. However, special voltage and current transformers are needed for these measurements which are technically demanding since they have to cope with the high voltages at the HV side and are therefore expensive.
Therefore, there is a need for a less expensive method and system to influence the HV characteristics at the POI for compliance with the grid code.